The use of mechanical resonators for measuring properties of materials, including liquid and vapor phases, has been disclosed in commonly-owned U.S. Pat. No. 6,336,353 (Matsiev, et al.)(“Method and apparatus for characterizing materials by using a mechanical resonator”); and U.S. Pat. No. 6,182,499 (McFarland, et al.) (“Systems and methods for characterization of materials and combinatorial libraries with mechanical oscillators”); and U.S. patent application Ser. Nos. 09/723,818, 09/800,819, and 09/133,171; published U.S. Patent Application No. 20030000291; and U.S. patent application Ser. No. 10/155,207 (“High Throughput Microbalance and Methods of Using Same”) (filed May 24, 2002), all of which are hereby expressly incorporated by reference for all purposes.
It has been observed that a preferred resonator is one that is operated at a relatively low frequency, e.g. below about 1 MHz; however, resonators may be operated at higher frequencies. For example, a highly preferred resonator is one that employs at least one cantilever end, and more preferably a plurality of cantilever ends, such as would be found in a tuning fork.
The above patent documents disclose the employment of various alternative resonators, such as tridents, cantilevers, torsion bars, bimorphs, or membrane resonators.
The documents also address the possibility of coating resonators with a coating for sensitivity to certain chemicals, wear resistance, for environmental protection or for some other functionality.
As the success of resonators for use in sensing applications has grown, the environments within which the resonators are expected to perform have likewise increased. In particular, the desire for increasing resonator life in high stress, abrasive and/or chemically aggressive environments has driven the search for improved specific material and structural combinations.